7. The abilityof birds to flydepends on
A. Their hollow hones only
B. Their flightfeathers only
C. Their feathers coveringtheir bodies
D. Their hollow bones andflightfeathers
E. Their light bodies only

9. Which ofthe followingstatements about machines is/aretrue?
I. The commonest and simplest of allmachines is thelever
II. The efficiencyof amachine is the ratio of work outputto work input
III. The efficiencyof amachine is usuallyless than one
IV. Machines makeworking much easierand convenient

26. The eclipse of themoon occurs when the
A. moon and thesun areinastraight line B. earth and the sunareinastraight line C. sun is between the earthand the moon D. earth is between the sunand the moon
E. moon comes between thesun and the earth